lkml.org 
[lkml]   [2021]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [RFC v2-fix-v2 2/2] x86/tdx: Ignore WBINVD instruction for TDX guest
On Mon, May 24, 2021 at 5:40 PM Andi Kleen <ak@linux.intel.com> wrote:
>
>
> On 5/24/2021 4:42 PM, Dave Hansen wrote:
> > On 5/24/21 4:32 PM, Kuppuswamy Sathyanarayanan wrote:
> >> Functionally only DMA devices can notice a side effect from
> >> WBINVD's cache flushing.
> > This seems to be trying to make some kind of case that the only visible
> > effects from WBINVD are for DMA devices. That's flat out wrong. It
> > might be arguable that none of the other cases exist in a TDX guest, but
> > it doesn't excuse making such a broad statement without qualification.
>
> We're describing a few sentences down that guests run with EPT
> IgnorePAT=1, which is the qualification.
>
> >
> > Just grep in the kernel for a bunch of reasons this is wrong.
> >
> > Where did this come from?
>
> Again the logic is very simple: TDX guest code is (mostly) about
> replacing KVM code with in kernel code, so we're just doing the same as
> KVM. You cannot get any more proven than that.
>

I have no problem pointing at KVM as to why the risk is mitigated, but
I do have a problem with misrepresenting the scope of the risk.

\
 
 \ /
  Last update: 2021-05-25 02:54    [W:0.287 / U:0.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site